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13 November 2014

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You are in: Essex > Places > Places features > Wind of change

Electricity substation at Gunfleet Sands

The substation sends power back to land

Wind of change

The view from the Essex coastline is set to change over the next year, as 48 wind turbines are erected on the Gunfleet Sands. We join the crew of the 'Cacheflow' whose job it is to look after the local marine life to find out more.

Love them or loathe them, off-shore wind farms are becoming an increasingly common site around the British coastline.

Wind farm monopile

The monopiles are driven up to 40m into the seabed

One of the latest of those is being built on Gunfleet Sands, approximately 4½ miles off the Clacton coastline, or 45 minutes by boat from Brightlingsea.

When completed in 2010, the wind-farm will comprise 48 turbines and one off-shore substation. The turbines will be roughly 900 metres apart and from sea level to the tip of the highest blade will stand 129 metres high.

The site will cover 17.5 square kilometres of seabed and should generate enough electricity for 120,000 houses.

The turbines will feed into the substation, which exports the electricity back to shore via a massive underground cable that runs in-land to Holland-on-Sea and meets up with the National Grid at Cooks Green.

Excalibur piling ship

Massive piling ship 'Excalibur' bangs in monopiles

The site is being built and will be run for its 25-year life-span by Danish company, DONG Energy.

Peter Sills, from the company, says locations such as Gunfleet Sands are ideal for utilising wind power.

"Being offshore allows us to have large turbines, at a greater distance, with less visual impact and less annoyance to everyone concerned," he says.

"It's on good construction ground; it's a sandbank so commercial vessels stay well clear of it, so from a safety point of view, the positioning of the wind farm is good.

Wind turbine

How the windfarm will look when complete

"It's also near to the shore so it's a short connection cable and there's a good wind regime as well in the area."

At the moment, there is an exclusion zone around the site, but once construction is completed, it will be open for boats to sail around them, fish, or just look at the imposing structures.

Blowing in the wind

There are many people who are against either wind farms for aesthetic or environmental reasons. There are also those who say it is not the most effective way of producing energy.

However, Peter argues this is increasingly not the case: "Renewable energy is definitely energy for the future. The wind farm is now a mature form of energy, it's something that can be easily financed and be produced.

Turbine monopiles

48 turbines will sit approx 900m apart

"Other forms of energy, such as tidal and wave energy are to some degree in their infancy. In five or 10 years time when they've been developed they will be bankable projects and then they will be built.

"Yes, wind is an intermittent form of energy, but we've looked at the data and we reckon we'll be able to produce electricity 80% of the time from this site and about 40% of the time at maximum capacity."

Off-shore mammal men

So far, much of the construction work has focused on installing the 48 monopiles, the bases which the turbines are fixed to, deep into the seabed. Hammering these 400 tonne structures into place has been done by huge 'jack-up barges'.

With these in place, the turbines can now be bolted into place and assembled over the next few months.

Crew of the Cacheflow

The crew of the Cacheflow

As well as DONG's own machinery and workforce, the Gunfleet Sands project is also utilising around 40 launches to assist in the construction work.

One of those is vessels in owned by Terry Batt, whose 40-foot boat 'Cacheflow' is usually used as a fishing charter vessel, but for now is being used to check for marine life around the wind-farm.

He says whilst it's like nothing he has done before, it has come along at a difficult time for fisherman and boat owners like him.

"It's totally different and very, very interesting and nice to know that the environment is being well and truly looked after," he explains.

Passive accoustic monitoring equipment

Receivers detect the presence of off-shore mammals

"Since DONG have moved into the area, it's kept local boatmen like myself employed, especially in times where people are facing the credit crunch and not so many can afford to go fishing, so this has been a lifeline to us."

Joining him on-board are marine mammal observers Mark Parry and Tom Gordon, whose job it is to monitor the presence of animals such as bottle-nosed dolphins, harbour porpoises and common seals.

"[We're here to] make sure they're not harmed by any of the excess noise that the piling operations would produce," explains marine mammal observer Mark.

"So we use visual surveillance for dolphins, porpoises and seals, as well as an acoustic survey of what's in the water so we can hopefully inform the construction guys that there's something about."

Acoustic monitoring computer

High frequencies are shown as bright coloured dots

Whilst Mark scans the surface of the water from the observation deck atop the Cacheflow, Tom uses special 'passive acoustic monitoring' equipment to check the depths of the north sea.

Using a 100 metre cable which houses two receivers that it cast off from the side of the boat, Tom is able to trace the area for any mammals.

"It listens for the vocalisations of the marine mammals and there's a sound card which samples the sound very quickly so we can hear very high frequencies.

He continues: "Porpoises vocalise at a very high frequency which is very similar to bats - about 130khz - which is way beyond our own hearing threshold.

The Cacheflow boat

The Cacheflow is usually used for fishing trips

"That's why we sample very high frequencies that we can't hear and the computer does the clever bit of looking for the signals within it."

The work the crew of the Cacheflow do is taken very seriously by the construction crews, as Tom explains: "When a detection is made, there will be a period where the piling and construction has to stop for about half-an-hour from the last sighting of any mammals that are going to get harmed.

"Luckily for the team of the project there have been very few. We've seen seals in transit to and from the site, but during the construction and immediately prior to it, there haven't been any sightings to cause a delay."

last updated: 23/03/2009 at 11:04
created: 19/03/2009

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